昆欄樹族群之遺傳變異及其相關類群親緣關係之研究

Study on the genetic variation of Trochodendron aralioides and its phylogenetic relationship with allies.

吳瑞娥(juei-er Wu)

指導教授 ： 童武夫 ； 王震哲

國立臺灣師範大學/理學院/生物學系/博士(2000年)

摘要

本論文的第一部份為研究東亞特有植物昆欄樹族群之遺傳結構，來探討該物種之遺傳變異度及基因流傳情形等微演化的情形。第二部份則利用分子歧異度的証據，來重新界定昆欄樹與其相關類群的分子親緣關係。
使用同功異構酵素、逢機擴大多型性核酸技術及ITS序列分析，探討東亞特有植物昆欄樹族群之遺傳結構。前者分析十九個族群，而ITS序列分析則分析二十個族群，共選取了十六個台灣本島之族群、兩個日本本島族群，及琉球群島的西表島與奄美大島（ITS序列分析）族群樣本。綜合三種遺傳標示的結果，昆欄樹族群內具有高的遺傳變異，主要導因於其特殊雌、雄差別成熟的花期及昆蟲傳粉行為所造成。族群間高度的遺傳歧異，則與地理的阻隔有相當的關連性。由於地質年代上長久的隔離，造成台灣與日本、奄美大島親緣關係較遠，而與近期隔離的西表島親緣關係較近。在同功異構酵素、逢機擴大多型性核酸技術及ITS序列分析中，都顯示出日本/奄美大島群及台灣/西表島群為區隔的兩群。因此，遺傳分化已經存在這兩大群，其間只有極少的基因流傳存在，明顯屬於地理割裂的隔離分化。而在台灣島內不同地理分區及山脈的阻隔，與族群間的遺傳分化有相關。台灣中部的族群，累積較多遺傳變異及具有較多的古老的祖先型，可能是冰期時昆欄樹族群的避難所，於冰期後再散佈到其他各地;而台灣南部里龍山及北部陽明山具有較低的遺傳變異，可能是冰期後昆欄樹族群散佈的邊緣地帶。我們的結果顯示日本與台灣族群間，適合隔離分化模型， 但台灣島內族群間並不符合此一模式，這些論點二組數據分析的結果皆相一致。
利用細胞核內5.8 S rDNA及葉綠體trnL（UAA）intron DNA、rbcL-atpb基因區間片段等序列，來測定分布於東亞的低等金縷梅類植物7科7個代表種的分子親緣關係。並加入高等金縷梅類胡桃科胡桃屬（Juglans）、榛木科千金榆屬（Carpinus）及虎皮楠科虎皮楠屬（Daphniphyllum）一併作對照分析，而以木蘭科烏心石屬（Michelia）為外群，用以界定其分子親緣關係。有關低等金縷梅類植物的分子親緣，綜合以上三組序列資料之比對分析，再加上已發表之18S rRNA （Hoot and Crane, 1996）及rbcL（Feng et al., 1998）序列分析之結果可歸納出下列結論： 1. 低等及高等金縷梅類植物來自共同祖先，而低等金縷梅類植物是並系群。2. Cercidiphyllum與金縷梅科關係密切，不應放在昆欄樹目，本研究結果支持將其併入金縷梅科（Hoot and Crane, 1996）。3. Tetracentron 應併入昆欄樹科。4. Euptelea和Trochodendron-Tetracentron 關係疏遠，反較近於Platanus。5. Platanus和金縷梅科關係疏遠，不同於形態研究所認定具共同祖先之看法。

關鍵字

同功異構酵素 ； 遺傳歧異度 ； 族群遺傳結構 ； 族群分化 ； 轉錄間區 ； 昆欄樹目 ； 親緣關係 ； 低等金縷梅類植物

並列摘要

Trochodendron aralioides Sieb. & Zucc., a species of the monotypic family Trochodendraceae is an evergreen tree characterized by vesselless wood. This primitive angiosperm is restricted to the East Asia in distribution. The purpose of this study is to investigate the population structure of this narrow distributed species and to explore the phylogeny of T. aralioides and its allies.
Multiple data of allozyme, and nucleotide sequences of the internal transcribed spacers (ITS) of ribosomal DNA were used to investigate genetic structure. Nineteen (allozyme) and twenty (ITS) populations were analyzed, including 16 from Taiwan, four from the main islands of Japan, Iriomote Island and Amami-O-shima. Genetic variability at the species level was comparable to that of narrow distributed species. In comparisons of allozyme, and ITS DNA sequences, the following results are concluded: first, genetic diversity was largely distributed within, rather than among, populations. Plants with protogynous and protandrous sexuality are highly self-incompatible, which probably promotes outcrossing and contributes to the high levels of heterozygosity within populations. Second, populations of T. aralioides were grouped into two distinct clusters, i.e., Japan/Amami-O-shima and Taiwan/Iriomote Island, indicating historical division undergone genetic differentiation. Populations of Iriomote Island was closely related to northern Taiwan. Those of glacial history of this area. Third, based on AMOVA analysis and no share an ITS haplotype, suggesting that geographic barriers have impeded gene flow. The genetic differentiation maybe due to geographic vicariance. Fourth, the isolation by distance model does not fit populations in Taiwan, but suitably describes the relationship between populations of T. aralioides in Japan and Taiwan.
In the second part, the phylogeny of representative species from seven families of the lower Hamamelidae was examined based on DNA sequences of 5.8S rDNA, trnL (UAA) intron and rbcL-atpb intergenic spacer. Three genera of the higher Hamamelidae, Juglans, Carpinus and Daphniphyllum were included. Cladistic analyses suggested paraphyly of the lower Hamamelidae, rooted at Michelia of Magnoliaceae. The 50% majority-rule consensus most parsimonious tree, maximum-likelihood tree and neighbor-joining tree were reconstructed using PAUP based on combined datas. All of the parsimonious trees of 1098 steps, with a CI and an RI of 0.837 and 0.691, respectively, were recovered. All reconstructed trees suggested that the lower Hamamelidae are a paraphyletic group. The Cercidiphyllaceae are most closely related to Hamamelidaceae, suggesting that Cercidiphyllaceae be placed in the Hamamelidales. Trochodendraceae and Tetracentraceae are very close as indicated by a bootstrap value of 100%. The Eupteleaceae phylogenetially are closely related with the Platanaceae.

並列關鍵字

Allozymes ； Genetic diversity ； Population genetic structure ； Population differentiation ； Internal transcribed spacer ； Trochodendrales ； Phylogeny ； Lower Hamamelidae

參考文獻

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